The present invention relates to electromagnetic brakes in general, and more particularly to improvements in electromagnetic brakes of the type wherein a first component or armature of the brake is secured to a rotary member (e.g., to the shaft of a motor, engine or another machine) and a second component of the brake is non-rotatably secured to a stationary member (such as a wall, bearing plate or an analogous part of a motor, engine or another machine). Still more particularly, the invention relates to improvements in electromagnetic brakes of the type wherein the second component of the brake comprises one or more solenoids which are energizable to establish and electromagnetic field serving to effect engagement or disengagement of the two components.
In heretofore known electromagnetic brakes of the above outlined character, the second component (including the solenoid(s)) is affixed to a stationary member in such a way that it is held against any movement, i.e., against angular movement as well as against movement in the axial direction of the first component. The first component shares the angular movements of the rotary member and is movable axially of the rotary member, i.e., toward the second component when the latter is caused to or is free to attract the first component. As a rule, the connection between the first component and the rotary member includes one or more springs which bias the first component axially and away from the second component. In other words, rotation of the first component (and of the rotary member, such as a shaft) can take place when the spring or springs are free to move the first component axially of the rotary member and away from the fixedly mounted second component of the brake.
The width of the customary air gap which is provided between the first component and the friction generating liner of the second component in disengaged condition of the brake varies as the wear upon the parts of the brake (especially upon the liner) progresses. The liner is mounted in the second component and frictionally engages a portion of the first component when the brake is operative, i.e. when the electromagnetic field is free to overcome the bias of the aforementioned spring or springs in order to maintain the two components of the brake in actual contact with each other. The effectiveness of the brake decreases as the width of the air gap increases; therefore, it is necessary to adjust the brake from time to time so as to reduce the width of the gap to an acceptable value, for example, by replacing a worn friction generating liner with a fresh liner. In most instances, the width of the air gap is reduced by shifting the first component of the brake axially of the rotary member in a direction toward the second component, i.e., toward the friction generating liner. Such operation is time-consuming and must be carried out by skilled attendants because it is necessary to dismantle the entire brake as well as a portion of the machine in which the brake is installed in order to gain access to the first component to an extent such as is necessary to enable the attendant or attendants to change the axial position of the first component with respect to the rotary member. As a first step, the attendant or attendants must remove the customary protective shield or housing for the brake in order to gain access to the first (rotary) component. The entire operation takes up inordinately large amounts of time, which unduly affects the output of the machine wherein the brake is put to use.
The situation is further aggravated if the electromagnetic brake is combined with an electromagnetic clutch. Such combinations are used in many machines. If the width of the air gap requires adjustment (as a rule, the adjustment involves a reduction of the width of the air gap), the clutch must be dismantled and removed before the attendants can gain access to the protective housing of or directly to the electromagnetic brake, especially to the axially movable first component of the brake. Upon completion of adjustment, the protective housing must be reinstalled prior to reassembly of the clutch with the adjusted brake. Moreover, and since the clutch also defines an air gap whose width is a function of the width of the air gap between the two components of the brake, each adjustment of the air gap in the brake necessitates a corresponding adjustment of the air gap in the clutch. These operations are time-consuming, even more so than if the electromagnetic brake is used alone, i.e., not in combination with an electromagnetic clutch.